Samples intended for official checking of the levels of benzo(a)pyrene in foodstuffs shall be taken according to the methods described below. Aggregate samples thus obtained shall be considered as representative of the lots. Compliance with maximum levels laid down in Regulation (EC) No 466/2001 shall be established on the basis of the levels determined in the laboratory samples.
‘Lot’: an identifiable quantity of a food commodity delivered at one time and having been determined by the official to have common characteristics, such as origin, variety, type of packing, packer, consignor or markings.
‘Sublot’: designated part of a lot in order to apply the sampling method on that designated part; each sublot must be physically separate and identifiable.
‘Incremental sample’: a quantity of material taken from a single place in the lot or sublot.
‘Aggregate sample’: the combined total of all the incremental samples taken from the lot or sublot.
‘Laboratory sample’: sample intended for the laboratory.
Sampling shall be performed by an authorised person as specified by the Member States.
Each lot which is to be examined must be sampled separately.
In the course of sampling and preparation of the samples precautions must be taken to avoid any changes, which would affect the benzo(a)pyrene content, adversely affect the analytical determination or make the aggregate samples unrepresentative.
As far as possible incremental samples should be taken at various places distributed throughout the lot or sublot. Departure from this procedure must be recorded in the record.
The aggregate sample is made up by uniting all incremental samples. This aggregate sample is homogenised in the laboratory unless this is incompatible with implementation of point 3.6.
Replicate laboratory samples for enforcement, trade (defence) and referee purposes shall be taken from the homogenised aggregate sample unless this conflicts with Member States’ rules on sampling.
Each sample shall be placed in a clean, inert container offering adequate protection from contamination and against damage in transit. All necessary precautions shall be taken to avoid any change in composition of the sample, which might arise during transportation or storage.
Each sample taken for official use shall be sealed at the place of sampling and identified following the Member State’s rules.
A record must be kept of each sampling, permitting each lot to be identified unambiguously and giving the date and place of sampling together with any additional information likely to be of assistance to the analyst.
The sampling method applied shall ensure that the aggregate sample is representative for the lot that is to be controlled.
In the case of oils, for which a homogeneous distribution of benzo(a)pyrene can be assumed within a given lot, it is sufficient to take three incremental samples per lot to form the aggregate sample. Reference to the lot number shall be given. For olive oil and olive pomace oil further information on sampling is given in Commission Regulation (EC) No 1989/2003(1).
For other products, the minimum number of incremental samples to be taken from the lot shall be as given in Table 1. The incremental samples shall be of similar weight, no less than 100g each, resulting in an aggregate sample of no less than 300g (see point 3.5).
Minimum number of incremental samples to be taken from the lot
Weight of lot (in kg) | Minimum number of incremental samples to be taken |
---|---|
< 50 | 3 |
50 to 500 | 5 |
> 500 | 10 |
If the lot consists of individual packages, then the number of packages which shall be taken to form the aggregate sample is given in Table 2.
Number of packages (incremental samples) which shall be taken to form the aggregate sample if the lot consists of individual packages
Number of packages or units in the lot or sublot | Number of packages or units to be taken |
---|---|
1 to 25 | 1 package or unit |
26 to 100 | About 5 %, at least 2 packages or units |
> 100 | About 5 %, at maximum 10 packages or units |
Sampling of foodstuffs at the retail stage should be done where possible in accordance with the above sampling provisions. Where this is not possible, other effective sampling procedures at retail stage can be used provided that they ensure sufficient representativeness for the sampled lot.
The control laboratory shall analyse the laboratory sample for enforcement in duplicate analyses in cases where the obtained result of the first analysis is less than 20 % below or above the maximum level, and in these cases shall calculate the mean of the results.
The lot is accepted if the result of the first analysis or, where duplicate analysis is necessary, if the mean does not exceed the respective maximum level (as laid down in Regulation (EC) No 466/2001) taking into account the measurement uncertainty and correction for recovery.
The lot is non-compliant with the maximum level (as laid down in Regulation (EC) 466/2001) if the result of the first analysis or, where duplicate analysis is necessary, if the mean exceeds the maximum level beyond reasonable doubt taking into account the measurement uncertainty and correction for recovery.
The basic requirement is to obtain a representative and homogeneous laboratory sample without introducing secondary contamination.
The analyst should ensure that samples do not become contaminated during sample preparation. Containers should be rinsed with high purity acetone or hexane (p.A., HLPC grade or equivalent) before use to minimise the risk of contamination. Wherever possible, apparatus coming into contact with the sample should be made of inert materials e.g. aluminium, glass or polished stainless steel. Plastics such as polypropylene, PTFE etc. should be avoided because the analyte can adsorb onto these materials.
All of the sample material received by the laboratory is to be used for the preparation of test material. Only very finely homogenised samples give reproducible results.
There are many satisfactory specific sample preparation procedures which may be used.
Finely grind (where relevant) and mix thoroughly the complete aggregate sample using a process that has been demonstrated to achieve complete homogenisation.
The replicate samples for enforcement, trade (defence) and referee purposes shall be taken from the homogenised material unless this conflicts with Member States’ rules on sampling.
A number of the most commonly used definitions that the laboratory will be required to use are given below:
=
Repeatability, the value below which the absolute difference between two single test results obtained under repeatability conditions (i.e., same sample, same operator, same apparatus, same laboratory, and short interval of time) may be expected to lie within a specific probability (typically 95 %) and hence .
=
Standard deviation, calculated from results generated under repeatability conditions.
=
Relative standard deviation, calculated from results generated under repeatability conditions .
=
Reproducibility, the value below which the absolute difference between single test results obtained under reproducibility conditions (i.e., on identical material obtained by operators in different laboratories, using the standardised test method), may be expected to lie within a certain probability (typically 95 %); .
=
Standard deviation, calculated from results under reproducibility conditions.
=
Relative standard deviation calculated from results generated under reproducibility conditions , where is the average of results over all laboratories and samples.
=
the observed RSDr divided by the RSDr value estimated from the Horwitz equation (1) using the assumption r = 0.66R.
=
the observed RSDR value divided by the RSDR value calculated from the Horwitz equation.
=
the expanded uncertainty, using a coverage factor of 2 which gives a level of confidence of approximately 95 %.
Methods of analysis used for food control purposes must comply with points 1 and 2 of the Annex to Council Directive 85/591/EEC.
Where no specific methods for the determination of benzo(a)pyrene in food are prescribed at Community level, laboratories may select any validated method provided the selected method meets the performance criteria indicated in the Table. The validation should ideally include a certified reference material.
Performance criteria for methods of analysis for benzo(a)pyrene
Parameter | Value/comment |
---|---|
Applicability | Food specified in Regulation (EC) No …/2005 |
Detection limit | No more than 0,3 μg/kg |
Limit of quantification | No more than 0,9 μg/kg |
Precision | HORRATr or HORRATR values of less than 1.5 in the validation collaborative trial |
Recovery | 50 %-120 % |
Specificity | Free from matrix or spectral interferences, verification of positive detection |
However, an uncertainty approach may also be used to assess the suitability of the method of analysis to be used by the laboratory. The laboratory may use a method which will produce results within a maximum standard uncertainty. The maximum standard uncertainty can be calculated using the following formula:
where:
is the maximum standard uncertainty
is the limit of detection of the method
is the concentration of interest
If an analytical method provides results with uncertainty measurements less than the maximum standard uncertainty the method will be equally suitable to one which meets the performance characteristics given in the Table.
The analytical result is to be reported corrected or uncorrected for recovery. The manner of reporting and the level of recovery must be reported. The analytical result corrected for recovery is used for checking compliance (see Annex I, point 5).
The analyst should note the ‘European Commission Report on the relationship between analytical results, the measurement of uncertainty, recovery factors and the provisions in EU food legislation’ (2).
The analytical result has to be reported as x +/– U whereby x is the analytical result and U is the measurement uncertainty.
Laboratories must comply with Directive 93/99/EEC.
Participation in appropriate proficiency testing schemes which comply with the ‘International Harmonised Protocol for the Proficiency Testing of (Chemical) Analytical Laboratories’ (3) developed under the auspices of IUPAC/ISO/AOAC.
Laboratories should be able to demonstrate that they have internal quality control procedures in place. Examples of these are the ‘ISO/AOAC/IUPAC Guidelines on Internal Quality Control in Analytical Chemistry Laboratories’ (4).
(http://europa.eu.int/comm/food/food/chemicalsafety/contaminants/index_en.htm).